调质态42Cr_2Mo钢堆焊特性研究

为了满足42Cr2Mo钢表面修复的需要,用贝氏体焊条堆焊调质态2Cr2Mo钢,研究了在不同的焊接电流和层间温度下焊缝的组织和性能。试验结果表明:贝氏体焊条的焊接性能好;焊接电流越大,组织越粗大;第一层熔敷金属的硬度比第二层的熔敷金属的硬度高。     

贝氏体钢辙叉专用焊条接头组织和力学性能

针对新型辙叉用贝氏体钢，研制出一种焊接工艺性能良好、焊缝组织为粒状贝氏体的、用于焊接修补和连接的专用焊条。通过分析焊接接头组织和力学性能，表明与辙叉母材的性能基本一致，能够满足使用要求。     

WDB620低碳微合金贝氏体无缝钢管焊接工艺研究

本文针对WDB620低碳微合金贝氏体无缝钢管,分别采用J507和J707Ni焊条通过选取不同的预热温度,焊接工艺参数,焊后热处理进行焊接试验,并进行了显微组织、力学性能、压力测试、接头探伤检验与分析。结果表明：WDB620低碳微合金贝氏体钢管采用J707Ni焊前预热,焊后回火,石棉保温缓冷等焊接工艺,利于焊缝金属和母材组织的过渡,着重解决了传统焊接冷却后产生延迟裂纹的倾向及接头性能不达标的缺陷,实验也说明适合的焊条型号,合理的焊接参数设置,正确的焊接工艺操作,适宜的焊后热处理工艺,对提高焊接性能和优化焊缝组织有显著效果。     

X80管线钢焊接接头组织及性能的研究

通过硬度测试及SEM观察,分析X80管线钢焊接接头处硬度和显微组织变化规律.受焊接热循环的影响,热影响区粗晶区组织主要为粗大的粒状贝氏体和板条贝氏体,硬度较高.靠近热影响区的基体,由于M/A岛分解,硬度值减小.外焊焊缝的显微组织主要是晶内形核铁素体、粒状贝氏体和多边形铁素体.靠近外焊焊缝的内焊焊缝组织受二次热循环的影响较大,组织为粒状贝氏体和块状的铁素体.远离外焊焊缝的内焊焊缝组织受二次热循环影响较小,组织和外焊焊缝组织相差不大.内焊组织中析出物的数量远大于外焊焊缝组织,析出强化效果显著,使内焊的硬度大于外焊的硬度.     

球铁焊缝金属贝氏体相变及组织结构特点

研究了球铁焊缝金属贝氏体相变及组织结构特点。试验结果表明，焊缝金属贝氏体相变依据等温时间不同分为三个阶段。第一阶段焊缝的基体组织为马氏体、贝氏体铁素体和残余奥氏体，第二阶段的组织为贝氏体铁素体和残余奥氏体，第三阶段的组织为贝氏体铁素体、残余奥氏体和碳化物。此外，还讨论了球铁焊缝金属贝氏体相变的有关机理     

86CrMoV7支承辊堆焊焊条堆焊工艺及性能的研究

研究了一种用于86CrMoV7钢支承辊修复的耐磨堆焊焊条。工艺试验表明,采用打底焊过渡层的方法可有效防止堆焊时出现裂纹,金相显微分析表明,研制的支承辊堆焊焊条的堆焊合金组织是马氏体基体和少量碳化物,性能测试结果表明,堆焊层的平均硬度在HRC52左右,满足86CrMoV7钢支承辊材料的硬度要求,耐磨性远大于86CrMoV7支承辊材料,是其耐磨性的36倍,可用于支承辊的修复堆焊。     

CrMoNbB系免预热耐磨料磨损堆焊焊条的研究

从硬度、金相组织、耐磨性、抗裂性等试验着手,分析堆焊层的显微组织结构,明确其合金化机理及形成条件,进而实现强化机构的量化设计,研制出综合性能优异的CrMoNbB系耐磨堆焊焊条.试验结果表明,堆焊层具有较高塑韧性,焊前不预热,焊后不缓冷,连续堆焊不产生裂纹;堆焊层硬度达到HRC55以上,具有较高的耐磨性,相对耐磨性优于D667焊条.     

15CrMoR钢材的焊接接头组织及其硬度分析

分别采用焊条R307和焊条A302在母材15CrMoR容器用钢上进行焊接试验。对焊缝金属和热影响区金属的显微组织进行了分析，并对焊接接头金属的硬度进行了测试。研究结果表明：15CrMoR钢采用焊条R307焊接，经焊后热处理的焊接接头的组织为铁素体、珠光体和碳化物，焊缝金属的硬度与母材的硬度相近。采用焊条A302焊接时，其焊缝组织为奥氏体和树枝状的δ铁素体，并存在枝晶偏析，在热影响区形成了贝氏体组织，是导致热影响区金属的硬度比焊缝区金属的硬度高得多的原因。     

45号钢堆焊熔敷金属的组织及性能

分别采用焊条CHR172和CHR132在基体材料45号钢上进行了堆焊试验；对焊缝金属和热影响区金属的显微组织进行了分析；对堆焊熔敷金属的硬度进行了测试。结果表明：堆焊金属的显微组织和显微硬度与焊条的种类和堆焊工艺参数有关。焊条CHR172堆焊熔敷金属的硬度比焊条CHR132堆焊熔敷金属的硬度好。     

NR360贝氏体耐磨钢板的组织与性能

研究南钢NR360贝氏体耐磨钢板的组织、力学性能、耐磨性能及焊接性能。结果表明,NR360耐磨钢板的组织为板条状的无碳化物贝氏体及残余奥氏体组织,该钢板具有较高的屈服强度、抗拉强度,及良好的韧性。钢板的耐磨性好,在滑动磨损试验下,钢板的磨损机制主要为微切削与犁沟机制。焊接接头中焊缝组织主要为块状和针状铁素体组织,热影响区组织为细化的板条贝氏体与马氏体组织。焊接接头具有良好的强韧性,热影响区的硬度与耐磨钢基体相近。     

Influence of isothermal bainitic processing on the mechanical properties and microstructure characterization of TRIP steel

The mechanical properties of transformation induced plasticity (TRIP) steel are strongly affected by the conditions of iso-thermal bainitic processing. The multiphase microstructure of TRIP steel under different conditions of isothermal bainitic processing was investigated using OM, SEM, XRD and TEM. The volume fraction of retained anstenite and the carbon content in anstenite were determined quantitatively using X-ray diffraction patterns. The relationship between mechanical properties and isothermal bainitic processing parameters was investigated. The stability of retained anstenite was analyzed by the volume fraction of retained austenite and the carbon content in retained anstenite. The experimental results show that the multiphase microstructure consists of ferrite,bainite and metastable retained austenite. To obtain good mechanical properties, the optimal conditions of isothermal bainitic tem-perature and holding time are 410-430℃ and 180-240 s, respectively. After isothermal bainitic processing under the optimal condi-tions, the corresponding volume fraction of retained anstenite is 5vol%-15vol%, which can provide enough retained austenite and plastic stability for austenite with high carbon content.     

重载铁路辙叉用新型贝氏体钢的应用基础研究

根据我国重载铁路辙叉发展要求,在已有发明应用的客运铁路贝氏体钢辙叉基础上,研究重载铁路辙叉用新型贝氏体钢,满足辙叉心轨大尺寸下,热处理空冷态得到贝氏体组织,获得高强高韧性能,代替传统高锰钢辙叉材料。研究表明:研制的新型重载辙叉心轨贝氏体钢成分设计实现了在正火空冷态获得奥氏体-贝氏体复合组织,贝氏体组织为无碳化物贝氏体;奥氏体-贝氏体复合组织具有优异的综合力学性能,断裂强度高达1 400 MPa,V型缺口的锻后回火态试样的冲击强度高达39.8 J。     

Refinement of packet size in low carbon bainitic steel by special thermo-mechanical control process

The packet size of bainitic steel can be refined by a special relaxation-precipitation-control phase transformation (RPC) technology, When processed by RPC process, the low carbon bainitic steel composes of two kinds of main intermediate transformation phases. One is ultra-fine lath-like bainitic ferrite and the lath is less than 1 tam in width and about 6 tam in length; the alignment of laths forms a refined packet, and the size of packets is about 5-7 ~am in length and about 3-4 tam in width, The other is acicular structure. The morphology and distribution of these acicular structures are influenced by relaxation process, the thin and short acicular structures cut the prior austenite grain and refine the bainitic packet size, For the optimum relaxation time, the packet size can be refined to the finest. The mechanical properties are influenced by relaxation time and the 800 MPa grade low carbon bainitic steel with excellent toughness can be obtained by RPC process,     

Study on laser welded heat-affected zone in new ultralow carbon bainitic steel

800 MPa grade ultralow carbon bainitic （NULCB） steel is the recently developed new generation steel, which was produced by thermo mechanical controlled processing ＆ relaxation-precipitation controlling transformation （TMCP＆RPC） tech- nique. The microstructure and the mechanical properties of the heat-affected zone （HAZ） in NULCB steel under laser welding conditions were investigated by using a Gleeble-1500 thermal simulator. The experimental results indicate that the simplex microstructure in the HAZ is granular bainite that consists of bainite-ferrite （BF） lath and M-A constituent when the cooling time from 800 to 500℃ （t8/5） is 0.3-30 s, and the M-A constituent consists of twinned martensite and residual austenite. As t8/5 increases, the hardness and tensile strength of HAZ decreases, but they are higher than that of the base metal, indicating the absence of softened zone after laser welding. The impact toughness of HAZ increases at first and then decreases when t8/5 increases. The impact energy of HAZ is much higher than that of the base metal when t8/5 is between 3 and 15 s. It indicates that excellent low temperature toughness can be obtained under appropriate laser welding conditions.     

热穿-热轧法生产的新型贝氏体中空渗碳钢的组织和性能

用热穿-热轧法制备了新型贝氏体中空钢．研究了热处理对新型贝氏体钢和渗碳处理对中空钢组织和性能的影响．结果表明：新型贝氏体钢正火＋低温回火热处理后的组织为贝氏体铁素体和奥氏体,淬火＋低温回火后的组织由马氏体、贝氏体和奥氏体组成;正火或淬火＋低温回火后,新型贝氏体中空钢具有良好的强韧性．正火＋低温回火后,中空钢的组织为贝氏体铁素体和残余奥氏体组织．新型贝氏体中空钢渗碳后空冷,渗层的组织为高碳马氏体和残余奥氏体组织,非渗层为贝氏体铁素体和残余奥氏体组织,实体中空钢具有较好的强韧性和渗碳效果．     

Effect of zirconium addition on the austenite grain coarsening behavior and mechanical properties of 900 MPa low carbon bainite steel

The ultra-free bainitic microstructure of a 900 MPa low carbon bainitic Cu-Ni-Mo-B steel was obtained by a newly developed relaxation precipitation control (RPC) phase transformation processing.In a pan-cake like prior-anstenite grain,the microstructure consisted of lath bainite,a little of abnormal granular bainite,and acicular ferrite.The effect of zirconium carbonitrides on the austenite grain coarsening behavior was studied by transmission electron microscopy (TEM).The results show that,the lath is narrower with increasing cooling rate.The ratio of all kinds of bainitic microstructure is proper with the intermediate cooling rate;and Zr-containing precipitates distribute uniformly,which restrains austenite grain growing in heat-affected welding zone.     

热冲压22MnB5硼钢中频电阻点焊接头组织及力学性能研究

对2mm热冲压22MnB5硼钢试样采用中频电阻点焊连接技术,利用合适的焊接参数开展了热冲压硼钢中频电阻点焊工艺研究.对比分析了其组织及力学性能,并对试样接头进行拉剪实验、十字拉伸实验,横截面进行了微观组织、硬度分布、断裂模式分析,初步找到热冲压硼钢中频电阻点焊不同焊接规范对焊接接头力学性能的影响规律.结果表明:合理的中频电阻点焊工艺下的焊接接头具有良好的力学性能,能满足实际生产需求.     

高速客车转向架构架焊接接头组织与力学性能

采用混合气体保护焊焊接方法对进口S355J2W钢和国产09CuPCrNi-A钢两种耐候钢通过焊接机器人单面焊双面成型的方式进行自动焊接实验,通过拉伸、硬度和金相检验试验方法对得到的焊接接头显微组织和力学性能进行了分析研究。结果表明,两种钢材焊接接头抗拉强度均优于母材,具有良好的力学强度,能够满足国产化技术要求。两种钢的焊接接头焊缝组织类似,S355J2W钢焊缝主要为粗大板条状和块状铁素体加先共析铁素体,含少量珠光体和粒状贝氏体;09CuPCrNi-A钢焊缝主要为条状和针状铁素体加先共析铁素体,含少量珠光体和粒状贝氏体。     

Effect of welding process on the microstructure and properties of dissimilar weld joints between low alloy steel and duplex stainless steel

To obtain high-quality dissimilar weld joints, the processes of metal inert gas (MIG) welding and tungsten inert gas (TIG) welding for duplex stainless steel (DSS) and low alloy steel were compared in this paper. The microstructure and corrosion morphology of dissimilar weld joints were observed by scanning electron microscopy (SEM); the chemical compositions in different zones were detected by en-ergy-dispersive spectroscopy (EDS); the mechanical properties were measured by microhardness test, tensile test, and impact test; the corro-sion behavior was evaluated by polarization curves. Obvious concentration gradients of Ni and Cr exist between the fusion boundary and the type II boundary, where the hardness is much higher. The impact toughness of weld metal by MIG welding is higher than that by TIG weld-ing. The corrosion current density of TIG weld metal is higher than that of MIG weld metal in a 3.5wt% NaCl solution. Galvanic corrosion happens between low alloy steel and weld metal, revealing the weakness of low alloy steel in industrial service. The quality of joints pro-duced by MIG welding is better than that by TIG welding in mechanical performance and corrosion resistance. MIG welding with the filler metal ER2009 is the suitable welding process for dissimilar metals jointing between UNS S31803 duplex stainless steel and low alloy steel in practical application.